Theoretical and experimental studies of multi-port RF power feeding in rod-type radio frequency quadrupole (RFQ) linac

Abstract

An analytical and experimental study of multi-port RF power feeding in a four rod-type radio frequency quadrupole (RFQ) has been discussed. First, we have derived generalized relations for multi-coupler power feeding based on S-parameters for n balanced couplers. Using simulation and measurements on a prototype, the optimum position and orientation of two and four couplers in an 80 MHz extended vane rod type RFQ have been determined. A low power RF test has been carried out to show the phase and power balancing using S parameter analysis for two and four mock-up couplers for the RFQ. As a corroborative study, the vane tip voltage measured with a vector voltmeter showed that voltage corresponding to power fed through a single coupler (β = 1) agrees with the value when the same power is fed using two or four couplers.